One of the subviews of a stack view not showing up at all

Question

I want my stack view to have three views: red image, blue image and register view. The thing is that while the red and blue button appear just fine, the register view does not.

This is how I set up and place my stack view inside my view controller view:

func setupSocialStackView() {
    let socialStackView = UIStackView(arrangedSubviews: redImage, blueImage, registerView])
    socialStackView.axis = .vertical
    socialStackView.distribution = .fillProportionally
    view.addSubview(socialStackView)
    socialStackView.spacing = 8

    // NSLayoutAnchor constraints here to place stack view 
    // inside my view controller view
}

This is the code for my register view which doesn't show up:

lazy var registerView: UIView = {
    let containerView = UIView()

    // Register button
    let registerButton = UIButton(type: .system)
    registerButton.setTitle("Register", for: .normal)
    registerButton.titleLabel?.font = UIFont.systemFont(ofSize: 12, weight: UIFontWeightLight)
    registerButton.titleLabel?.textAlignment = .center
    registerButton.setTitleColor(UIColor.black, for: .normal)
    registerButton.titleLabel?.textColor = UIColor(r: 91, g: 90, b: 90)
    registerButton.addTarget(self, action: #selector(presentRegisterController), for: .touchUpInside)
    containerView.addSubview(registerButton)

    return containerView
}()

The other two arrange views of the stack view are UIImageViews.

Why are the two images there and the register view is not? Am I missing something?

Answer 1

You don't appear to be giving your UIButton a frame size. See what you get if you add an autoresizingMask line:

    registerButton.addTarget(self, action: #selector(presentRegisterController), for: .touchUpInside)

    registerButton.autoresizingMask = [.flexibleWidth, .flexibleHeight]

    containerView.addSubview(registerButton)

Answer 2

For me, I needed to add bottom, right, and left constraints for the view inside the stack view. Then it appeared.